Work feeding mechanisms for sewing machines



y 23, 1967 M. R. LAIDIG 3,320,913

WORK FEEDING MECHANISMS FOR SEWING MACHINES Filed Jan. 4, 1965 I NVE NTOR.

v BY Manfred R. Laidig WITNESS 5o 5O 49 Q? 1 C TTORNEY United States Patent Jersey Filed Jan. 4, 1965, Ser. No. 423,131 4 Claims. (Cl. 112---215) This invention relates to work feeding mechanisms for sewing machines and more particularly to a drop feed or four-motion work feeding mechanism for sewing machines in which the conventional mechanism for effecting feed lift is eliminated.

In sewing machines employing conventional drop feed or four-motion work feeding mechanisms, motion is imparted to the work feeding mechanism through two sets of driving connections, a work feed-lift driving mechanism and a work feed-advance driving mechanism, in order to impart to the feed dog its characteristic fourmotion movements of lift, feed advance, drop and feed return. Coordination of the foregoing work feed driving mechanisms requires a large number of parts in order to generate the complex feed-lift and drop motions. Moreover, the operation of a conventional work feed lift driving mechanism materially adds to the vibration of the sewing machine during it operation as the feed dog transmits through the work repeated hammer blows against the bottom of the presser foot.

It is, therefore, an object of this invention to provide an improved work feeding mechanism for sewing machines which eliminates the necessity for providing a conventional work feed-lift driving mechanism, thus reducing the number of parts in the machine.

Another object of the invention is to provide a work feeding mechanism for sewing machines which causes less vibration of the machine than do conventional work feeding mechanisms.

To fulfill the objects of the invention, the feed dog is mounted on a feed plate by means of four identical links. The feed plate is in turn slidably mounted on the bottom of the throat plate to receive rectilinear reciprocating motion from the work feed-advance driving mechanism. Two light springs tend to bias the feed dog upwardly on the links through the feed slots in the throat plate to initiate the engagement of the feed teeth with an article of work fabric. When the feed plate is reciprocated in the direction of feed, the resistance offered by the work fabric held by the presser foot causes the feed dog to further rise up on the links through slots in the throat plate whereupon the feed teeth firmly engage the work fabric in opposition to the presser foot to accomplish feeding of the fabric. When the feed plate is reciprocated in the opposite direction, the links collapse against the light spring pressure thus permitting the feed dog to drop to a level where the feed dog lightly rubs on the work during the feed-return motion.

Other objects and a fuller understanding of the invention may be had by referring to the following description and claims, taken in conjunction with the accompanying drawings in which:

FIG. 1 is a fragmentary cross sectional view of a worksupporting bed of a sewing machine incorporating a work feeding mechanism of the invention;

FIG. 2 is an enlarged cross sectional view of the work feeding mechanism of FIG. 1 showing how the feed dog rises; and

FIG. 3 is an exploded bottom perspective view of the work feeding mechanism of FIG. 1.

With reference to the drawing, a work feeding mechanism incorporating the invention is illustrated as eml and 14 of the U-shaped feed plate 11.

3,320,913 Patented May 23, 1967 bodied in a sewing machine having a frame including a work-supporting bed 10.

The work feeding mechanism includes a U-shaped feed plate 11 having a forward base portion 12 and two trailing limb portions 13 and 14. Four small identical links 15, 16, 17 and 18 are pivotally mounted on the opposed innermost sides 19 and 20 of the limb portions of the U-shaped feed plate forming two rows, each row containing two links mounted in tandem. The four links 15 to 18 are pivotally connected to the limb portions by means of four small pivot pins 21, 22, 23 and 24, respectively.

Carried by the two rows of links 15 to 18 is a feed dog 25 having three rows of feed teeth 26, 27 and 28. The four links 15 to 18 are pivo-tally connected to the outer sides of the outermost rows of fee-d teeth 26 and 28 by means of four small pivot pins 29, 30, 31 and 32, respectively, with the links within each row positioned parallel to each other.

cantilevered in two grooves 33 formed in the base portion 12 of the feed plate 11, as for example by solder, are spring means represented by two leaf-springs 34 having distal ends 35 which bear against the outermost rows of feed teeth 26 and 28. The distal ends 35 of the springs are adapted lightly to bias the feed dog 25 up on the four links 15 to 18. In order to limit the upward pivotal movement of the links, abutment means represented by lateral abutments 36 and 37 having vertical abutment surfaces 38 and 39 are formed on the opposed innermost sides 19 and 20 of the limb portions 13 and 14 of the feed plate 11. The vertical abutment surfaces 38 and 39 are so positioned with respect to the two forward-most pivoted links 15 and 16 that the forward links will bear against the abument surfaces 38 and 39 when all the links 15 to 18 have achieved a vertical position. Therefore, the links cannot go to an over-center position.

The feed plate 11 is slidably mounted on the bottom surface 40 of a throat plate 41. The throat plate has three feed slots 42, 43 and 44- corresponding to the three rows of feed teeth 26 to 28, respectively, of the feed dog 25, and the outermost feed slots 42 and 44 have widened portion 45 and 46, respectively, to accommodate the tops of the four links 15 to 18. Two threaded bores 47 are also formed in the throat plate.

In order to mount the feed plate 11 on the bottom surface 40 of the throat plate 41 for slidable movement, an elongated slot 48 is formed in each limb portion 13 The feed plate is connected to the bottom surface of the throat plate, with the rows of feed teeth 26 to 28 of the feed dog 25 in line with the feed slots 42 to 44, respectively, in the throat plate, by two shoulder screws 49 having head portions 50, shoulder or hearing portions 51, and threaded portions 52. Shoulder rivets could be employed in lieu of the shoulder screws 49. The bearing portions 51 of the shoulder screws 49 are placed in the elongated slots 48 in the feed plate 11 and the threaded portions 52 of the shoulder screws are screwed into the threaded bores 47 in the throat plate 41. The enlarged head portions 50 of the shoulder screws are adapted to retain the feed plate against the bottom surface 40 of the throat plate because the head portions 50 have diameters which are greater than the widths of the elongated slots 48.

In order to mount the throat plate 40 on the worksupporting bed 10 of the sewing machine, the throat plate has two grooves 53 of which only a part of one is shown. By means of the two grooves 53, the throat plate with the work feeding mechanism attached may be removably mounted on the work-supporting bed in a manner disclosed in the United States patent of R. E. Johnson, No. 2,920,593, granted Jan. 12, 1960. The throat plate closes a mechanism-access hole or opening 54 in the work-supporting bed.

Depending from the bottom of the base portion 12 of the feed plate 11 are two mounting pins 55 whereby the work feeding mechanism can be removably connected to a work feed-advance driving mechanism mounted in the work-supporting bed 10. The work feed-advance driving mechanism includes a feed bar 56 having two holes 57 formed in a distal end 58 to accommodate the depending mounting pins 55 on the feed plate. The feed bar is pivotally connected to a rock arm 59 which is in turn connected to an oscillating feed-advance rrock shaft 60. In order to support the feed bar 56 and to prevent binding of the feed bar during its oscillating movements, a bearing 61 having a convex curvilinear bearing surface 62 is mounted in the work-supporting bed. The convex bearing surface 62 of the bearing 61 slidably and rockably supports the bottom surface of the distal end of the feed bar.

As illustrated in FIGS. 1 and 2 a work fabric 63 is urged downwardly on the throat plate 41 by the sole plate 64 of a conventional presser foot 65 which is biased downwardly from the sewing machine frame and is arranged to overlie the feed dog 25.

In operation, when the feed plate 11 is shifted to the right, as viewed in FIG. 1, at the beginning of a feed stroke, the feed dog 25 is elevated on the pivoted links 15 to 18 into light engagement with the work fabric 63 because of the initial impetus of the springs 34 which bear against the bottom of the feed dog 25. As the feed plate 11 begins to shift toward the left as viewed in the drawings, the feed teeth 26 to 28 emerge from the slots 42 to 44 in the throat plate 41 above the level of the top surface of the throat plate because the feed teeth 26 to 28 grip the bottom surface of the article of work fabric 63 causing the pivoted links 15 to 18 to turn toward the vertical. Further movement of the feed plate 11 to the left increases the grip of the feed teeth on the work fabric as the pivoted links achieve a vertical position limited by the abutment surfaces 38 and 39 of the lateral abutments 36 and 37 formed on the limb portions 13 and 14 of the feed plate. In the above described feed stroke, the feed teeth grip the work fabric in a wedging action in opposition to the sole plate 64 of the presser foot 65.

When after completion of the feed advance stroke, the feed plate 11 is shifted to the right, the feed dog collapses against the light upward force exerted by the springs 34 and the feed teeth 26 to 28 are urged to, or slightly below, the level of the top surface of the throat plate 41 to accomplish a return stroke without back feeding. The shape of the feed dog teeth and the inertia of the feed dog 25 with respect to the feed plate 11 assist in the disengagement of the feed teeth 26 to 28 from the work material 63 during the return stroke.

The shallow depth of the work feeding mechanism from the tops of the feed teeth 26 and 28 to the bottom of the feed plate 11, in contrast to a work feeding mechanism having a conventional work feed-lift driving mechanism, prevents crowding of a loop-taker 66 mounted in the Work-supporting bed 10.

The work feeding mechanism can be modified to accomplish reverse feeding by providing a connection (not shown) to the feed dog 25, or to the pivoted links 15 to 18, whereby the pivoted links can be flipped beyond a vertical position to an over-center position. The lateral abutments 36 and 37 formed on the limb portions 13 and 14 of the feed plate 11 would be replaced by an adjustable lateral abutment (not shown) whereby the upward pivotal movement of the pivoted links 15 to 18 could be limited as they approach a vertical position from either side of the vertical position. Also, the feed teeth 26 to 28 could be formed with equilateral sides.

Although the invention has been described in its preferred form with a certain degree of particularity, it is understood that the present disclosure of the preferred form has been made by way of example and that numerous changes in the details of construction and the combination and arrangement of parts may be resorted to without departing from the spirit and the scope of the invention.

Having thus set forth the nature of the invention, what is claimed herein is:

1. A four-motion work feeding mechanism for a sewing machine for work fabric having a frame including a work-supporting bed having at least one slot therein, a presser foot having a sole plate and mounted on said frame with the sole plate opposing the slot in the worksupporting bed, and a work feed-advance driving mechanism mounted in the work-supporting bed, said Work feeding mechanism comprising a feed plate slidably mounted in the work-supporting bed for rectilinear reciprocating movement and connected to the work feedadvance driving mechanism to receive reciprocating movement, a plurality of links pivotally connected in tandem to the feed plate, a feed dog having at least one row of feed teeth and pivotally connected to said links with the feed teeth in line with the slot in the work-supporting bed, means for moving the feed dog up on said links through the slot in the work-supporting bed and slightly above the top surface of the work-supporting bed to initiate the gripping of an article of work fabric in opposition to said presser foot, and means for limiting said upward pivotal movement of said links.

2. A four-motion work feeding mechanism for a sewing machine for work fabric having a frame including a work-supporting bed having an opening therein, a throat plate having. at least one slot therein and adapted to be removably mounted on the work-supporting bed with the slot positioned over the opening in the Work-supporting bed, a presser foot having a sole plate and mounted on said frame with the sole plate adapted to oppose the slot in the throat plate, and a work feed-advance driving mechanism mounted in the work-supporting bed, said work feeding mechanism comprising a feed plate slidably mounted on the bottom surface of the throat plate for rectilinear reciprocating movement and adapted to be connected to the work feed-advance driving mechanism to receive reciprocating movement, a plurality of links pivotally connected in tandem to the feed plate, a feed dog having at least one row of feed teeth and pivotally connected to said links with the feed teeth in line with the slot in the throat plate, means for moving the feed dog up on said links through the slot in the throat plate and slightly above the top surface of the throat plate to initiate the gripping of an article of work fabric in opposition to said presser foot, and means for limiting said upward pivotal movement of said links.

3. A four-motion work feeding mechanism for a sewing machine for work fabric having a frame including a work-supporting bed having an opening therein, a throat plate having at least one slot therein and adapted to be removably mounted on the Work-supporting bed with the slot positioned over the opening in the work-supporting bed, a presser foot having a sole plate and mounted on said frame with the sole plate adapted to oppose the slot in the throat plate, and a work feed-advance driving mechanism mounted in the work-supporting bed, said Work feeding mechanism comprising a feed plate slidably mounted on the bottom surface of the throat plate for rectilinear reciprocating movement parallel to the top surface of the throat plate and adapted to be connected to the work feed-advance driving mechanism to receive reciprocating movement, a plurality of identical links pivotally connected in tandem to the feed plate forming at least one row of links, each row of links containing only two links, a feed dog having at least one row of feed teeth and pivotally connected to said links with the feed teeth in line with the slot in the throat plate, means for biasing the feed dog up on said links through the slot in the throat plate and slightly above the top surface of the throat plate to initiate the gripping of an article of work fabric in opposition to said presser foot, and abutment means for limiting said upwa-rd pivotal movement of said links short of an over-center position.

4. A four-motion work feeding mechanism for a sewing machine for work fabric having a frame including a worksupporting bed having an opening therein, a throat plate having at least two slots therein and adapted to be removably mounted on the work-supporting bed with the slots positioned over the opening in the work-supporting bed,

a presser foot having a sole plate and mounted on said 10 frame with the sole plate adapted to oppose the slots in the throat plate, and a work feed-advance driving mechanism mounted in the work-supporting bed, said work feeding mechanism comprising a feed plate slidably mounted on the bottom surface of the throat plate for rectilinear reciprocating movement parallel to the top surface of the throat plate and adapted to be connected to the Work feed-advance driving mechanism to receive reciprocating movement, four identical links pivotally connected in tandem in two rows to the feed plate, a. feed dog having at least two rows of feed teeth and pivotally connected to said links with the links mutually parallel and with the feed teeth in line with the slots in the throat plate, spring means for lightly biasing the feed dog up on said links through the slots in the throat plate and slightly above the top surface of the throat plate to initiate the gripping of an article of Work fabric in opposition to said presser foot, and abutment means for limiting said upward pivotal movement of said links short of an over-center position.

References Cited by the Examiner UNITED STATES PATENTS 16/ 1936 Cundall et a1 112-215 5/ 1939 Christensen et a1. 112215 

1. A FOUR-MOTION WORK FEEDING MECHANISM FOR A SEWING MACHINE FOR WORK FABRIC HAVING A FRAME INCLUDING A WORK-SUPPORTING BED HAVING AT LEAST ONE SLOT THEREIN, A PRESSER FOOT HAVING A SOLE PLATE AND MOUNTED ON SAID FRAME WITH THE SOLE PLATE OPPOSING THE SLOT IN THE WORKSUPPORTING BED, AND A WORK FEED-ADVANCE DRIVING MECHANISM MOUNTED IN THE WORK-SUPPORTING BED, SAID WORK FEEDING MECHANISM COMPRISING A FEED PLATE SLIDABLY MOUNTED IN THE WORK-SUPPORTING BED FOR RECTILINEAR RECIPROCATING MOVEMENT AND CONNECTED TO THE WORK FEEDADVANCE DRIVING MECHANISM TO RECEIVE RECIPROCATING MOVEMENT, A PLURALITY OF LINKS PIVOTALLY CONNECTED IN TANDEM TO THE FEED PLATE, A FEED DOG HAVING AT LEAST ONE ROW OF FEED TEETH AND PIVOTALLY CONNECTED TO SAID LINKS WITH THE FEED TEETH IN LINE WITH THE SLOT IN THE WORK-SUPPORTING BED, MEANS FOR MOVING THE FEED DOG UP ON SAID LINKS THROUGH THE SLOT IN THE WORK-SUPPORTING BED AND SLIGHTLY ABOVE THE TOP SURFACE OF THE WORK-SUPPORTING BED TO INITIATE THE GRIPPING OF AN ARTICLE OFF WORK FABRIC IN OPPOSITION TO SAID PRESSER FOOT, AND MEANS FOR LIMITING SAID UPWARD PIVOTAL MOVEMENT OF SAID LINKS. 